150 lines
4.5 KiB
C
150 lines
4.5 KiB
C
/*-------------------------------------------------------------------------
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*
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* hsearch.h--
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* for hashing in the new buffer manager
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*
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*
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* Copyright (c) 1994, Regents of the University of California
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*
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* $Id: hsearch.h,v 1.9.2.1 1999/03/07 02:01:09 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef HSEARCH_H
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#define HSEARCH_H
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/*
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* Constants
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*
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* A hash table has a top-level "directory", each of whose entries points
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* to a "segment" of ssize bucket headers. The maximum number of hash
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* buckets is thus dsize * ssize (but dsize may be expansible). Of course,
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* the number of records in the table can be larger, but we don't want a
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* whole lot of records per bucket or performance goes down.
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*
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* In a hash table allocated in shared memory, the directory cannot be
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* expanded because it must stay at a fixed address.
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*/
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#define DEF_SEGSIZE 256
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#define DEF_SEGSIZE_SHIFT 8 /* log2(SEGSIZE) */
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#define DEF_DIRSIZE 256
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#define DEF_FFACTOR 1 /* default fill factor */
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#define PRIME1 37 /* for the hash function */
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#define PRIME2 1048583
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/*
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* Hash bucket is actually bigger than this. Key field can have
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* variable length and a variable length data field follows it.
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*/
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typedef struct element
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{
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unsigned long next; /* secret from user */
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long key;
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} ELEMENT;
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typedef unsigned long BUCKET_INDEX;
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/* segment is an array of bucket pointers */
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typedef BUCKET_INDEX *SEGMENT;
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typedef unsigned long SEG_OFFSET;
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typedef struct hashhdr
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{
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long dsize; /* Directory Size */
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long ssize; /* Segment Size --- must be power of 2 */
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long sshift; /* Segment shift */
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long max_bucket; /* ID of Maximum bucket in use */
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long high_mask; /* Mask to modulo into entire table */
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long low_mask; /* Mask to modulo into lower half of table */
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long ffactor; /* Fill factor */
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long nkeys; /* Number of keys in hash table */
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long nsegs; /* Number of allocated segments */
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long keysize; /* hash key length in bytes */
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long datasize; /* elem data length in bytes */
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long max_dsize; /* 'dsize' limit if directory is fixed size */
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BUCKET_INDEX freeBucketIndex;
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/* index of first free bucket */
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#ifdef HASH_STATISTICS
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long accesses;
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long collisions;
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#endif
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} HHDR;
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typedef struct htab
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{
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HHDR *hctl; /* shared control information */
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long (*hash) (); /* Hash Function */
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char *segbase; /* segment base address for calculating
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* pointer values */
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SEG_OFFSET *dir; /* 'directory' of segm starts */
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long *(*alloc) (); /* memory allocator (long * for alignment
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* reasons) */
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} HTAB;
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typedef struct hashctl
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{
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long ssize; /* Segment Size */
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long dsize; /* Dirsize Size */
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long ffactor; /* Fill factor */
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long (*hash) (); /* Hash Function */
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long keysize; /* hash key length in bytes */
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long datasize; /* elem data length in bytes */
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long max_dsize; /* limit to dsize if directory size is
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* limited */
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long *segbase; /* base for calculating bucket + seg ptrs */
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long *(*alloc) (); /* memory allocation function */
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long *dir; /* directory if allocated already */
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long *hctl; /* location of header information in shd
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* mem */
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} HASHCTL;
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/* Flags to indicate action for hctl */
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#define HASH_SEGMENT 0x002 /* Setting segment size */
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#define HASH_DIRSIZE 0x004 /* Setting directory size */
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#define HASH_FFACTOR 0x008 /* Setting fill factor */
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#define HASH_FUNCTION 0x010 /* Set user defined hash function */
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#define HASH_ELEM 0x020 /* Setting key/data size */
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#define HASH_SHARED_MEM 0x040 /* Setting shared mem const */
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#define HASH_ATTACH 0x080 /* Do not initialize hctl */
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#define HASH_ALLOC 0x100 /* Setting memory allocator */
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/* seg_alloc assumes that INVALID_INDEX is 0*/
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#define INVALID_INDEX (0)
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#define NO_MAX_DSIZE (-1)
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/* number of hash buckets allocated at once */
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#define BUCKET_ALLOC_INCR (30)
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/* hash_search operations */
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typedef enum
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{
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HASH_FIND,
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HASH_ENTER,
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HASH_REMOVE,
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HASH_FIND_SAVE,
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HASH_REMOVE_SAVED
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} HASHACTION;
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/*
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* prototypes from functions in dynahash.c
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*/
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extern HTAB *hash_create(int nelem, HASHCTL *info, int flags);
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extern void hash_destroy(HTAB *hashp);
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extern void hash_stats(char *where, HTAB *hashp);
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extern long *hash_search(HTAB *hashp, char *keyPtr, HASHACTION action,
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bool *foundPtr);
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extern long *hash_seq(HTAB *hashp);
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extern long hash_estimate_size(long num_entries, long keysize, long datasize);
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/*
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* prototypes from functions in hashfn.c
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*/
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extern long string_hash(char *key, int keysize);
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extern long tag_hash(int *key, int keysize);
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#endif /* HSEARCH_H */
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